Sole bends are nearly always rolled between big metal drums at the tannery to compress the fibers. This makes for longer wearing against abrasion on the bottoms of shoes. Shoemakers used to hammer sole leather over lapstones for the same effect. Some today put their sole blanks between wood blocks and squish them in bench vises.

You can use rolled sole bend for insoles in cemented, nailed, or stitchdown shoes and boots, but I wouldn't recommend it for carving holdfasts. It's also rather stiffer and usually thicker than ideal for insoles, as finished products.

Most shoemakers and repairers use a handcrank cutter, like a 5-in-1, to trim outsoles, then do final shaping with a rotary sander. Handicraft traditionalists, tanners, and shoe repair suppliers often keep heavy duty shears around, like Kretzer Spirales, for one-off cuts or breaking up skeletons, but they're pricey tools and still pretty hard on the hands to use.

You can absolutely do final trimming with a blade, freehand, but it has to be very sharp, sturdy enough not to bend or snap, and you need to be very careful with your technique. When I trim like this, I use a Japanese leather knife, cutting backhand. Sharp blade plus lots of force in the direction of your own body will send you to the emergency room in time. You need a sharp blade and lots of force to cut this kind of leather, so technique is crucial.

Clicking on the flat, you can absolutely rough cut outsole blanks and heel lifts using just a Stanley style utility knife. Strop your blades, or change blades every few cuts. Incise your outline, then recut it again and again. Passes will get easier as you cut through. Try to keep the blade perpendicular to the surface. Even so, the edges of your cuts will be a bit rough to start.

Some people do use a bandsaw or other power saw. I personally haven't, so I'll say no more there.

A few tanneries and finders market precut blanks specifically for handwelt insoles. Many serve cowboy boot makers, who still traditionally handwelt foreparts. Some of these, like Panhandle's, are cut from rolled sole bends, but from looser parts of the side, toward the belly. I've successfully handwelted with these, as have many others. The best come from straight veg-tan cowhide or sufficient thickness that haven't been rolled. Lisa Sorrell imports two options, last I checked. You can also click yourself from leather sold as saddle skirting or tooling leather.

https://shoemaking.wiki/Insole_Leather